The separation and isolation of blood components from a whole blood sample is a significant aspect of the treatment and clinical and laboratory testing of such blood components. There are numerous methods and apparati for the separation of blood components.
Whole blood can be separated by low speed centrifugation into a cell free fluid called serum (or if a blood anticoagulant is present) and a pellet containing cells and platelets. Serum is about 92% water and contains electrolytes, lipoproteins, proteins, hormones, other nutrients and vitamins. The lipoproteins are lipid-protein complexes. Lipoproteins are the primary transport molecules for lipids and also transport vitamin E and beta-carotene (provitamin A). Lipoproteins are further divided into very low density lipoprotein, low density lipoprotein and high density lipoprotein. High levels of low density lipoprotein are associated with atherosclerosis and cardiovascular disease. In contrast, high levels of high density lipoprotein are thought to protect against atherosclerosis.
The primary proteins found in plasma are albumin, globulins, fibrinogen. Albumin is the most abundant plasma protein (about 60%) and is a carrier molecule for nonesterified fatty acids. Albumin also plays a role in maintaining the osmotic pressure of blood. The globulins are further divided into alpha-, beta-, and gamma-globulins. The gamma-globulin fraction contains molecules that function as antibodies in the humoral immune system. Fibrinogen functions in clot formation.
The red blood cell (or erythocyte) is the primary cell found in blood. This unique cell has a membrane but no other membranous organelles and does not have a cell nucleus. The primary function of red blood cells is oxygen transport to tissues and the removal of carbon dioxide. The oxygen carrying molecule in the red blood cell is hemoglobin. The red blood has a biconcave shape and is extremely deformable and able to move through very small capillaries. In anemia, the number of red blood cells in a given volume of blood is low resulting in a decreased ability to deliver oxygen to tissues. Nutritional and/or genetic factors can contribute to anemia.
Blood also contains white blood cells and platelets. White blood cells (or leukocytes) include monocytes, lymphocytes, neutrophils, eosinophils, and basophils. Neutrophils, eosinophiles, and basophils (all three are also called granulocytes) as well as monocytes are phagocytic cells. Phagocytic cells and lymphocytes play a key role in the immune system. Platelets function in clot formation.
Since blood components have magnetization properties, there have been numerous efforts to utilize magnetism to separate and isolate such blood components. The most common problems with the prior art is that they cannot perform the separation in a continuous manner and they do not use a multi-dimensional gradient. In addition, the prior art does not provide a decoupling process and some of the prior art conduct separation in a static stage rather than a constant flow stage.
U.S. Pat. No. 4,910,148 to Sorenson et al. relates to a method and device for separating magnetized particles from biological fluids, particularly white blood cells using a monoclonal antibody to link the cells to magnetic beads. In contrast to the present invention, the Sorenson separation is static (i.e., no flow) and is conducted in a plastic blood bag. The magnetic beads are linked to the cancer white cells by an agitation process and then a magnetic field is applied to keep the white blood cells with the magnetic beads in the disposable plastic bag. The Sorenson device also requires space between the magnets which does not optimize the magnetic gradient (magnetic force). The back plate of the Sorenson device is a soft magnetized material and the magnets are Samruim-Cobalt. Sorenson has a volume limitation since it uses a blood bag (150 ml) and there is no decoupling between the beads and the white blood cells. Matter of fact, the cells remain in the disposable blood bag after separation.
U.S. Pat. No. 5,514,340 to Lansdorp, et al. relates to a device for separating magnetically labeled cells in a sampleusing an applied magnetic field. Lansdorp uses magnetized screens to attract the magnetic particles allowing the biological fluid to be caught in the magnetic wires of the screen. The magnets used in Lansdorp must constantly be cleaned since there is contact between the magnets and the blood cells.
U.S. Pat. No. 5,567,326 to Ekenberg et al. relates to an apparatus and methods for separating magnetically responsive particles from a non-magnetic test medium in which the magnetically responsive particles are suspended. In Ekenberg, small patch amounts of biological fluid are placed in a tube then a magnetic pin is inserted in the fluid for separation.
U.S. Pat. No. 5,541,072 to Wang et al. relates to methods and devices for separation of magnetic particles and/or magneticassociated substances from non-magnetic associated substances and media. Unlike the present invention, the Wang method does not utilize the optimum magnetic gradient (magnetic force) available since Wang situates its magnets on two opposing sides.
U.S. Pat. No. 4,988,618 to Li et al. relates to a magnetic separation device for use in immunoassay or hybridization assay procedures. The Li device comprises a base having a plurality of orifices for receiving nonferrous containers which hold the sample and the assay components including ferrous particles. The orifices are surrounded by a plurality of magnets which are spaced about the peripheral of the orifices.
U.S. Pat. No. 4,935,147 to Ullman et al. relates to a method for separating a substance from a liquid medium, particularly applicable for cells and microorganisms from aqueous suspension and also for the determination of a analyte. Although Ullman discusses a method with a reversible non-specific coupling, the method is not continuous nor does it utilize a multi-dimensional gradient.
The presently claimed invention overcomes the above mentioned problems by providing a system, an apparatus and a method for continuous separation of components from a mixture of chemical entities using a multi-dimensional gradient.